This experiment included 240 one-day old growing Japanese quail,  divided randomly into 6 groups, which were subdivided into two replicates with 20 chicks each. Chicks were fed from one day to six weeks of age diets contained 20 % crude protein for the first three groups and  24% for the other ( 4 – 6 ) groups. Each diet was supplemented with 0 , 1.0 or 1.50 g N-FAC 1000 / Kg diet in a 2x3 factorial design to evaluate their influences on the performance, digestibility, carcass and some blood constituents of growing Japanese quail. Results obtained revealed that increasing protein level from 20 to 24 % significantly improved the growth performance, carcass weights and economic efficiency. N-FAC 1000 supplementation improved the above parameters as well as the crude protein digestibility, total blood protein and albumin. Significant improvement was also recorded due to the interaction between dietary protein and N-FAC supplementation. However the better improvement was obtained by using the lower level of dietary crude protein.